1. Field of the Invention
The present invention relates to an ink supply device capable of removably mounting an ink cartridge and, more specifically, to an ink supply device capable of performing a reliable ink supply operation from the ink cartridge when the mounted ink cartridge is opened to the outside atmosphere. The present invention also pertains to an inkjet image recording device having the above-described ink supply device.
2. Description of Related Art
In general, a known inkjet recording device records an image on a conveyed recording medium by ejecting ink drops from a recording head mounted on a carriage. The carriage is movable in a main scan direction perpendicular to the direction of conveyance. Ink is stored in advance in a removable cartridge type ink tank, e.g., an ink cartridge, and supplied from the ink cartridge to the recording head. Ink cartridges are generally divided broadly into on-carriage types and off-carriage types, depending on the installation position of the cartridge in the inkjet recording device. The on-carriage type has a case having a mounting portion for removably mounting an ink cartridge provided on a carriage which is movable, as described above. Ink is supplied from the ink cartridge, mounted, and held within the mounting portion of the case to a recording head. In contrast, the off-carriage type has a case having a mounting portion for removably mounting an ink cartridge provided in a housing of an inkjet recording device at a location other than the movable carriage. Ink is supplied from the ink cartridge to a recording head through an ink supply tube.
Typically, in the known ink cartridge, if gas is dissolved in the ink to be supplied to the ink reservoir, the gas in the ink forms bubbles in the recording head. These bubbles may cause the nozzles to clog during recording, which may deteriorate printing performance. In order to prevent this, ink is supplied to the ink reservoir in a deaerated state. To maintain this state, the inside of the ink reservoir is maintained in a negative, or reduced below atmospheric, pressure state.
In both the known on-carriage type and the known off-carriage type, when the ink cartridge is set within the mounting portion, if the ink supply valve is opened first, air and ink accumulated in the mounting portion flows back to the ink reservoir, because the inside of the ink reservoir is in a negative pressure state. This may cause meniscus formed at a nozzle of the recording head to break. Known inkjet printer systems include an ink cartridge and a mounting portion provided in a housing. In known inkjet printer systems, the ink cartridge includes an ink reservoir, an ink supply valve for supplying ink, and an air communication recess covered with a sealing film to be torn for communication of the ink reservoir with the atmospheric air. Known inkjet printer systems feature an air communication protrusion for tearing the sealing film, or a hollow air intake for pushing the air communication valve to open it to the atmospheric air, and an ink intake to be connected to the ink supply valve for drawing out ink from the ink reservoir. In known inkjet printer systems, these are installed on the base portion of the mounting portion, upright, parallel, and extending in a direction opposite to the insertion direction of the ink cartridge. In known inkjet printer systems, the air communication protrusion is larger than that of the ink intake, such that the ink cartridge is opened to the atmospheric air before ink starts to flow from the ink cartridge.
Nevertheless, in this known inkjet system, the difference in protrusion amount between the air communication protrusion or the air intake and the ink intake may be small, which may lead to complications in operation. If the operation speed for inserting the ink cartridge into the mounting portion is rapid, the time between the introduction of air into the air communication valve and the connection of the ink intake to the ink supply valve becomes substantially zero, because there is little time difference therebetween. Thereupon, although the ink reservoir is still in a negative pressure state, the ink supply valve is opened, and as described above, air or ink accumulated in the mounting portion flows back into the ink reservoir. This may cause a breakage of the meniscus in the nozzle of the recording head and degrade printing performance.
Further, in a known inkjet system, if the ink cartridge is inserted at an angle with respect to the mounting portion, the connection of the ink intake to the ink supply valve may be established before opening of the air communication portion, so that the ink reservoir is may be placed in a negative pressure state. Thereupon, under an affection of the negative pressure within the ink cartridge, ink in the recording head flows back into the ink cartridge via the ink supply valve, and the meniscus in the nozzle of the recording head may be broken. This may result in a large amount of air being accumulated within the recording head, which may cause a defective ink supply operation.
For the purpose of solving the above-described problems, if an air communication protrusion is lengthened to increase the protrusion amount thereof, the air communication protrusion may be deformed or broken when the ink cartridge is inserted with the posture inclined, or if the ink cartridge is accidentally dropped. Furthermore, if the air communication protrusion is lengthened, the ink cartridge is required to have a large space for accommodating the long air communication protrusion when the ink cartridge is mounted on the mounting portion. As a result, because the size of the ink cartridge itself may increase, the size of the ink supply also may increase, or the capacity to store ink in the ink cartridge may decrease.